The present invention relates to a method of driving an ink jet head and an apparatus for driving an ink jet head.
An ink jet head has ink outlet ports. The head ejects ink supplied from an ink reservoir through the ink outlet ports to print data on a recording medium. If the ink jet head is left unused for a long time, water or volatile constituent evaporates from the ink in the outlet ports, increasing the viscosity of the ink or forming a solid film at the air-ink interface in the outlet ports. This makes it difficult to eject the ink through the outlet ports. Thus, once the ink jet heat has been left unused for a long time, it may fail to eject ink to print data. Even if the head ejects the ink, it cannot apply the ink in the desired direction and cannot achieve high-quality printing of data.
Jpn. Pat. Appln. KOKAI Publication No. 6-31932 discloses an ink jet head which has groups of nozzles and in which ink is ejected through the nozzles of each group, some time after ink has been ejected through those of the immediately preceding group. If the ink jet head is left unused for a long time, ink is ejected first through the odd-numbered nozzles and then through the even-numbered nozzles upon lapse of a predetermined time. This preliminary ink ejection washes away the ink clogging the nozzles, so that fresh ink may be smoothly ejected through the nozzles to print data.
Such preliminary ink ejection as is disclosed in Publication No. 6-31932 wastes ink in large quantities, particularly in an ink jet head of line type, which has a great number of nozzles.
An object of the present invention is to provide a method of driving an ink jet head to perform preliminary ink ejection without wasting ink too much, thus reliably keeping the ink outlet ports free from clogging, thereby to smoothly eject ink through the ink outlet ports.
Another object of the invention is to provide an apparatus for driving an ink jet head to perform preliminary ink ejection without wasting ink too much, thus reliably keeping the ink outlet ports free from clogging, thereby to smoothly eject ink through the ink outlet ports.
According to the first aspect of the invention, there is provided a method of driving an ink jet head which has ink chambers, energy-generating elements provided in the ink chambers, respectively, and ink outlet ports communicating with the ink chambers, respectively, and which ejects ink through the ink outlet ports by applying a drive pulse to the energy-generating elements, thereby to record data. The method comprises the steps of: forcing ink outwards from each of the ink outlet ports upon lapse of a predetermined time from formation of a meniscus in the ink outlet port, thereby increasing a surface area of the ink from a surface area of the meniscus; applying a negative pressure in each of the ink chambers, thereby drawing the ink back into the ink chamber and forming a meniscus again in the ink outlet port; and applying the drive pulse to each of the energy-generating elements, while the meniscus remains in each of the ink chambers, thereby ejecting ink from each of the ink outlet ports and recording data.
According to the second aspect of the invention, there is provided an apparatus for driving an ink jet head which has ink chambers, energy-generating elements provided in the ink chambers, respectively, and ink outlet ports communicating with the ink chambers, respectively, and which ejects ink through the ink outlet ports by applying a drive pulse to the energy-generating elements, thereby to record data. The apparatus comprises: timer means for starting measuring time when a meniscus is formed in each of the ink outlet ports; and preliminary drive means for performing preliminary drive by applying the drive pulse to each of the energy-generating elements a predetermined number of times when the time measured by the timer means reaches a preset value, thereby forcing ink outwards from each of the ink outlet ports and increasing a surface area of the ink from a surface area of the meniscus, and then by applying a negative pressure in each of the ink chambers. The drive pulse is applied to each energy-generating element after the preliminary drive means has performed the preliminary drive, thereby ejecting ink from each of the ink outlet ports and recording data.
The method according to the invention drives an ink jet head to perform preliminary drive control, without wasting ink too much, thus reliably preventing clogging in each ink outlet port to achieve stable recording of data.
The apparatus according to the invention drives an ink jet head to perform preliminary drive control, without wasting ink too much, thus reliably preventing clogging in each ink outlet port to accomplish stable recording of data.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.